The invention relates to a flat material for manufacturing leaf-like sheets for receiving information, comprising at least one coating applied onto the sheet material, wherein the coating comprises fine cavities. The invention also relates to writing devices for sheet material with a coating in which magnetizable particles are embedded.
Numerous embodiments of flat sheet material for manufacturing leaf-like writing sheets are known wherein such sheets are provided as information carriers whose information contents is designed for optical recognition by means of toner particles applied to the surface. The information is generally in the form of a text comprised of letters or of graphic elements such as drawings or the like. The sheet is generally made of paper comprising cellulose fibers or plastic fibers embedded in a binder or made of a plastic film which is used, for example, for overhead projection. The application of the color is realized by hand with corresponding writing utensils or by printing devices. The information contents combinable on a sheet is generally limited by the readability of, for example, smaller letters.
With the increasing spread of computers, in particular, in office technology, the interaction of optical and electronic information carriers gains increasingly in importance. Modern computer-controlled laser and magnetographic printers enable a resolution of more than 1,000 dpi (dots per inch, dots per approximately 2.54 cm). However, the human eye recognizes only characters which are comprised of a plurality of such dots so that the resolution that is available for a maximum information contents cannot be used. On the other hand, it may be required to convert optically recognizable information into electronic information. For this purpose, text documents are placed onto a so-called scanner and scanned electro-optically. The resulting electronic image of the original requires a large memory space. By means of a subsequent OCR or OMR software (Optical Character Recognition, optical letter recognition; Optical Mark Reading, reading of handwritten or printed marks) the dot information read by the scanner can be converted into character or letter information which causes a significant reduction of the space required in the memory. However, this conversion is time-consuming and requires, according to the present state of the art, generally a manual correction.
A further possibility of conversion of optical recognizable electronic data can be realized by MICR (Magnetic Ink Character Recognition) wherein character recognition is carried out by sensing standardized magnetic fonts in a magnetic toner. According to a further known method, information can be optically recognized in the form of a so-called bar-code comprising a system of stripes of different width and different spacing to one another, for example, fixed on an adhesive label, which can then be scanned by a reading pen or hand-held or long-range scanners. A disadvantage of the aforementioned system is the permanency of once printed information.
The copying of text documents is usually performed by means of photocopying wherein the toner information on a written sheet is optically scanned and transferred onto a drum. In this connection, by means of the so-called magnetographic method the drum is locally magnetically conditioned such that on the corresponding locations of the drum a toner powder adheres and is applied as a copy of the original onto an additional sheet. However, soiling that occurs occasionally can negatively affect the quality of the copy.